A Jacksonville law firm's claim that marijuana is already legal as medicine in Florida has other supporters of medical pot crying foul.

Health Law Services, formally incorporated as IJC Law Group, is telling clients that Florida's alternative health-care laws already say that doctors can prescribe otherwise-illegal drugs such as marijuana if they determine it is the only practical medicine for the patient.

So, the firm argues, Florida does not need to change the law or impose a constitutional amendmenttomake marijuana a legal treatment.

"It is clear that our Florida statute allows for the lawful possession of cannabis if somebody is in the possession of a prescription," said Christopher Ralph, legal administrator at Health Law Services.

The firm arranges, for $799, to send clients to doctors. If they find a medical necessity, the firm provides a letter certifying that the client has received a marijuana prescription and warning law enforcement officers against violating the client's rights.

The firm has signed up a couple of hundred such clients, including some in Central Florida, Ralph said.

But that legal interpretation and approach has led to arrests of Health Law Service clients. And it has brought rebukes from other medical marijuana advocates who say the law firm is giving people bad legal advice that could land them in prison.

"They are misleading clients and the public into believing that citizens have a right to use marijuana medicinally, when all they have is the right to assert that as a legal defense in court of law after they have been arrested and prosecuted," said Norm Kent, a Fort Lauderdale lawyer who has been practicing marijuana criminal defense law for 40 years. He also is past president of the nation's largest marijuana advocacy group, National Organization for the Reform of Marijuana Laws.

"They are charging people $800 for medical ID cards that are worthless," he said.

On Monday the firm also drew a blast from St. Johns County Sheriff David B. Shoar, who called a news conference about last month's arrests of a St. Johns County couple in possession of certification letters and 40 marijuana plants. Scott and Marsha Yandell, both 45, are charged with four felony marijuana charges, including trafficking.

"If there was a law that allowed for medical marijuana, I guess everybody in the state has missed it," Shoar said. "And two, they weren't trying to just produce medical marijuana. This was an industrial grow house."

Health Law Services, whose president is lawyer Ian Christensen, is defending the Yandells.

Ralph, a non-lawyer who speaks for the firm, said the Yandells did what they were supposed to do to meet the state's alternative health-care laws. Law enforcement and court officials, he said, simply need to be educated about the law. He said the letters are intended to do just that on behalf of each client.

Florida law does provide for a medical-necessity defense, but it is a tough sell to prosecutors, judges and juries, Kent and others said.

That defense was used to win a felony marijuana possession trial in Broward County this month. Other cases have led prosecutors to drop charges. But other attempts have sent people to prison.

Lawyers such as Kent and Michael Minardi of the law firm Kelley Kronenberg, who won the Broward case on March 2, take on such clients only after they have been arrested, rather than advising clients in advance that they can grow marijuana and win if arrested.